How many join channels could support phoenix websocket js

Hey dude! i have a question about how many channel joins could support a browser before it start to pause or consume all the resources. Do you know how could i do a good test for it? recently i am working in a project where could be more than 500 joins, i am sure that phoenix could support it in backend but not much in the browser. the view start to be slow but only in development because in production it works great. what do you think? thank you in advance guys!